Sound absorptive protective mat

ABSTRACT

The present invention concerns an automotive protective mat ( 1 ), also known as throw in mat or protective mat. This mat comprises a microporous stiffening layer ( 2 ) (acoustical membrane). This layer may be composed of several sheets. The overall air flow resistance is between 500 Ns/m 3 –4000 Ns/m 3 . It is essential for this mat ( 1 ) that it is hydrophobic. In order to achieve an enhanced acoustical effectiveness a decoupling layer ( 6 ) is foreseen between the microporous stiffening layer ( 2 ) and the vehicle floor ( 8 ). This decoupling layer might be incorporated in the mat ( 1 ) or constituted by the underlaying carpet or sound absorber of the vehicle floor. Further layers or sheets such as adhesive layers, non skid layers, face fabrics or carpets and/or loft layers can be added to the claimed mat.

This application claims the benefit of Provisional Application No.60/292,345, filed May 22, 2001.

FIELD OF THE INVENTION

The present invention relates to a sound absorptive protective mat forthe noise reduction in vehicles and relates to a combination of thissound absorptive protective mat with a conventional floor mat, inparticular with a multi-layered assembly package in accordance with U.S.Pat. No. 6,145,617, comprising a microporous stiffening layer.

BACKGROUND OF THE INVENTION

Automotive protective mats are usually placed over the fitted carpetingin motor vehicles and currently serve only to protect the carpetingunder the driver's and passengers' feet. They generally are notsignificantly sound absorbent. These known mats may even increase thenoise levels in the automobile, if they comprise a sound insulatinglayer which reflects the interior noise or if they are in resonance withthe underlying flooring. The acoustically enhanced protective matsdescribed below reduce the sound levels in a vehicle significantly. Themats described can be made lighter than currently produced protectivemats, thereby reducing the vehicle weight. The protective mat accordingto the invention can also be used in residential and commercialstructures to reduce the echoing in rooms with hard floors.

Existing automotive protective mats are well known in the art. Most ofthem consist of carpets having a fairly heavy backing layer and showpoor sound absorptive properties which are commonly compensated by anundesirable increased thickness of the backing layer.

SUMMARY OF THE INVENTION

It is therefore the object of the present invention to provide a thinand lightweight protective mat having superior acoustical properties.

In particular, it is the object of the present invention to provide aprotective mat to be used with conventional spring-mass flooring systems(showing a sound insulation loss in the range of resonance frequencies)or with conventional sound absorptive carpets (without sound insulationloss in the range of resonance frequencies), known from U.S. Pat. No.6,145,617.

This object is achieved by a protective mat with reference to theteaching of U.S. Pat. No. 6,145,617. This patent discloses anultra-light, multifunctional sound-insulating kit for reducing noise inmotor vehicles. This kit comprises a microporous reinforcing layercomprising an air flow resistance between R_(t)=500 Ns/m³ and R_(t)=2500Ns/m³, an areal-mass of m_(F)=0.3 kg/m² to m_(F)=2.0 kg m² and a bendingstiffness of B=0.05 Nm to B=10.5 Nm. This assembly package permits toreplace classic spring-mass-systems for noise reduction in vehicles andpermits to reduce the weight of these classic spring-mass-systems by atleast 50%. This kit does not behave like a conventional spring-masssystem and does not show a sound insulation loss in the range ofresonance frequencies. The content and teaching of U.S. Pat. No.6,145,617 is incorporated herein by way of reference.

The present invention aims to create a light weight floor mat to beplaced over the fitted carpeting and having an enhanced acousticaleffectiveness compared to known protective mats. The mentioned aims areachieved by a protective mat comprising a low air flow resistance andwater impermeable layer to be put on the vehicle floor, in particular tobe put on fitted carpeting, preferably a carpeting with a high loftlayer in accordance with U.S. Pat. No. 6,145,617. On top of this loftlayer there is fixed a face fabric or carpet (if needed) by means of atleast one adhesive layer (if needed). In addition, the present matcomprises at least one hydrophobic layer which can at the same time bean open cell layer to create a well defined air flow resistance.

The protective mat according to the invention is a further developmentof the multilayer assembly as disclosed in U.S. Pat. No. 6,145,617. Itis essential for the invention that a decoupling layer is providedbetween the protective mat and the vehicle carpeting or flooring. Thedecoupling layer can be incorporated in the mat or consists of a toplayer of the vehicle carpeting.

This invention and further preferred embodiments will be described withthe aid of the Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a sectional view of a preferred embodiment of a mataccording to the invention;

FIG. 2 shows a sectional view of second embodiment of a mat according tothe invention;

FIG. 3 shows a sectional view of an enhanced third embodiment of a mataccording to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a sectional view of a preferred embodiment of the soundabsorptive protective mat 1 incorporating a decoupler 6 and comprising ahydrophobic and air flow resistant layer 2. This hydrophobic and airflow resistant layer 2 carries optionally a face fabric or carpet 3,which both are permeable to air, and are preferably bonded by anadhesive layer 4; the face fabric or carpet 3 can also be mechanicallyfixed to the hydrophobic and air flow resistant layer 2. The hydrophobicand air flow resistant layer 2 can be fibrous or made of TPE(elastomer), rubber or vinyl. Underneath this hydrophobic and air flowresistant layer 2 there is foreseen a high loft, low air flow resistancelayer 5, comprising at its bottom an additional non-skid barrier layerfunctioning as a decoupler 6. This high loft, low air flow resistantlayer 5 is preferably attached to the hydrophobic and air flow resistantlayer 2 with the aid of a second adhesive layer 7.

The combination of the face fabric 3, the adhesive layers 4 and 7, andthe hydrophobic air flow resistant layer 2 has a total air flowresistance of 500 Ns/m³ –4000 Ns/M³. The hydrophobic layer 2 is able torepel sufficient moisture to protect the mat's internal structure andthe underlying carpet. Water resistance can also be achieved by anadhesive layer, in particular by a DOW 936, 0.0015″ adhesive film. Therepellent value averages 150 mm, in particular the layer shows no waterleakage for 150 ml per 6 hours or even 750 ml per 16 hours. The air flowresistant layer 2 is preferably made of tightly packed fibrous materialsin order to achieve a high bending stiffness. The stiffness ispreferably in the range of 0.05–10.5 Nm and is made of an open-poredmoulded rubber or an air permeable thermoplastic elastomer.

The high loft layer 5 is preferably made of a lofty fibrous layercomprising 3-denier fibres, but can also be made of open cell foam. Thethickness of this layer 5 determines the mat's effectiveness to absorblow frequency sound. When this high loft layer is made of polyurethanefoam or similar material, this layer functions also as a non-skid layer.If the high loft layer 5 does not provide acceptable non-skid and/orbarrier properties, then an additional non-skid barrier layer or othermechanical restraints may be provided.

FIG. 2 shows a mat in accordance with the present invention including anacoustical membrane only for interacting with an underlying carpet andsound absorber comprising a decor layer functioning as a decoupler 6.This mat 1 comprises a stiff hydrophobic and air flow resistant layer 2and optionally a face fabric or carpet 3. This face fabric or carpet 3is bonded to the hydrophobic and air flow resistant layer 2 by means ofan air permeable, adhesive layer 4. This embodiment reduces theinvention to the minimum structure. The protective layer 2 consists of atightly packed fibre layer, or a microporous rubber, TPE, vinyl orsimilar. The face fabric and adhesive layer are optional. The air flowresistance of this assembly should be between 500 Ns/m³–4000 Ns/m³,preferably between 500 Ns/m³ and 2000 Ns/m³. When mounted, theunderlying carpet and/or absorber (for instance according to U.S. Pat.No. 6,145,617,) functions as the decoupler layer for this assembly.Mechanical restraints of this mat may be necessary, depending upon thematerials used and the customers' requirements.

The following tables show the acoustical improvement of the mataccording to the present invention in comparison to classical mats witha closed surface. These calculations are based on the followingconfigurations:

Table 1:

values of a simple light weight carpet (in the following called “RULcarpet”) in accordance with U.S. Pat. No. 6,145,617 having the followingstructure:

-   -   0.8 mm steel    -   3.5 kg/m² bitumen damping    -   0.2 mm air gap    -   25 mm foam    -   0.7 kg/m² air flow resistant layer with AFR=1500 Ns/m³    -   4 mm carpet        are compared with an assembly of such an RUL carpet with the        addition of a protective mat according to the invention, which        RUL carpet comprises:    -   0.8 mm steel    -   3.5 kg/m² bitumen damping    -   0.2 mm air gap    -   10 mm foam    -   0.7 kg/m² air flow resistant layer with AFR=1500 Ns/m³    -   4 mm carpet, generating a 0.2 mm air gap        and which protective mat comprises the following structure:    -   15 mm foam, 0.7 kg/m², 1500 Ns/m³    -   4 mm carpet

TABLE 1 (2) RUL 10 mm foam, (1) Simple RUL 25 mm +protective mat 15 mmfoam, foam, 0.7 kg/m², 1500 Ns/m³ each 0.7 kg/m², 1500 Ns/m³ FrequencyTL α NR TL α NR (Hz) (dB) (1) (dB) (dB) (1) (dB) 60 16.0 0.16 8.0 16.50.15 8.3 100 19.5 0.13 10.6 20.0 0.13 11.1 160 23.5 9.17 15.8 23.0 0.2016.0 200 24.5 0.26 18.6 24.0 0.33 19.2 400 33.0 0.66 31.2 35.0 0.74 33.7800 46.5 0.76 45.3 48.5 0.73 47.1 1000 50.0 0.76 48.8 50.0 0.73 48.62000 50.0 0.76 48.8 50.0 0.76 48.8 3000 50.0 0.76 48.8 50.0 0.77 48.94000 50.0 0.77 48.9 50.0 0.77 48.9 5000 50.0 0.77 48.9 50.0 0.78 48.98000 50.0 0.76 48.8 50.0 0.77 48.9Table 2:values of a conventional RUL carpet carrying a protective mat accordingto the invention and having the following structure:

-   -   0.8 mm steel    -   3.5 kg/m² bitumen damping    -   0.2 mm air gap    -   20 mm foam    -   0.7 kg/m², 1500 Ns/m³ AFR layer    -   4 mm carpet, generating a 0.2 mm air gap        and    -   5 mm foam    -   0.7 kg/m², 1500 Ns/m³ AFR layer    -   4 mm carpet        are compared with a combination of a conventional RUL carpet        carrying a classical mat having the following structure:    -   0.8 mm steel    -   3.5 kg/m² bitumen damping    -   0.2 mm air gap    -   20 mm foam    -   0.7 kg/m², 1500 Ns/m³ AFR layer    -   4 mm carpet, generating a 0.2 mm air gap        and    -   5 mm foam    -   0.5 kg/m² resp. 4.0 kg/m² heavy layer    -   4 mm carpet

TABLE 2 RUL 20 mm Foam 5 mm Foam RUL 20 mm Foam 5 mm Foam 0.7 kg/m²,1500 Ns/m³ 0.5 kg/m², 96000 Ns/m³ 0.7 kg/m², 1500 Ns/m³ 4.0 kg/m², 96000Ns/m³ +Option Mat +Classical Mat +Option Mat +Classical Mat Frequency TLα NR TL α NR TL α NR TL α NR (Hz) (dB) (1) (dB) (dB) (1) (dB) (dB) (1)(dB) (dB) (1) (dB) 60 16.5 0.15 08.3 16.5 0.16 08.5 17.0 0.15 8.8 17.50.12 08.3 100 20.0 0.14 11.5 19.5 0.14 11.0 20.0 0.14 11.5 19.0 0.1410.5 160 23.0 0.20 16.0 22.0 0.20 15.0 24.0 0.26 18.1 16.0 0.60 13.8 20024.0 0.34 19.3 23.0 0.32 18.1 26.5 0.38 22.3 22.0 0.50 19.0 400 35.00.74 33.7 31.0 0.78 29.9 37.0 0.60 34.8 46.0 0.14 37.5 800 50.0 0.7048.5 50.0 0.34 45.3 49.5 0.64 47.6 50.0 0.18 42.6 1000 50.0 0.70 48.550.0 0.30 44.8 50.0 0.65 48.1 50.0 0.21 43.2 2000 50.0 0.74 48.7 50.00.36 45.6 50.0 0.72 48.6 50.0 0.27 44.3 3000 50.0 0.77 48.9 50.0 0.3845.8 50.0 0.76 48.8 50.0 0.32 45.1 4000 50.0 0.78 48.9 50.0 0.38 45.850.0 0.77 48.9 50.0 0.35 45.4 5000 50.0 0.78 48.9 50.0 0.39 45.9 50.00.77 48.9 50.0 0.37 45.7 8000 50.0 0.78 48.9 50.0 0.42 46.2 50.0 0.7748.9 50.0 0.40 46.0For these configurations the transmission loss (TL) and the absorptioncoefficient (α) have been calculated with a program called SISAB fordiffuse sound incidence. Noise reduction (NR) has been obtained usingthe formulaNR=10*log(α)+TLwhich is valid within a space with diffuse sound fields.

From these tables it becomes apparent that the combination in accordancewith the present invention results in significantly better acousticalperformance (insertion loss and absorption) with substantial weightreduction of the whole system as compared to classical (mass-backed,i.e. spring-mass) systems.

In-vehicle analysis shows that the protective mats according to theinvention the interior sound pressure levels and, more specifically,increase the on index values by 1%–2% for both powertrain noise andtire/road noise Furthermore, the combination in accordance with theinvention leads to a reduction of 27%.

Further preferred embodiments, as described below, have an overallthickness of 13 mm.

Such a first preferred embodiment consists of a 3 lb/ft³ and 6 mm thickPUR-foam adhered to a 4 mm thick polyester needled felt having a weightof 750 gr/m². The polyester felt comprises bicomponent melt fibres toachieve the required air flow resistance. The felt is treated with awater repellent to prevent moisture from penetrating. A carpet isadhered to the top of this hydrophobic and air flow resistant felt.

Such a second embodiment comprises 40 g/m² melt-blown polypropylenefibres to achieve the desired air flow resistance. The foam thickness isincreased to 9.5 mm to make up a 13 mm overall thickness.

Both embodiments show similar advantageous acoustic properties.

FIG. 3 shows a further developed embodiment of the present inventioncomprising the following structure from the bottom to the top:

-   -   a loft layer 10. This loft layer can be a die cut needled felt,        a die cut thermoplastic felt, a die cut non-hexa resinated felt,        a molded thermoplastic felt, a cast foam or a die cut slab foam;    -   a PET felt 11 with fluorocarbon treatment which is bonded to the        loft layer 10 by means of a spray hot melt 12;    -   an adhesive film 13 carrying a PET secondary scrim 16;    -   a PE pre-coat 14 carrying a carpet 15 with a PET primary        backing.

This structure allows to form the entire mat in a single-step processand may be manufactured with standard carpet molding equipment.Furthermore, with this assembly it is possible to avoid the use ofphenolic resin. In order to improve the water resistance of thisstructure the hydrophobic and air flow resistant felt is treated with afluorocarbon-based water repellent.

In summary, the present invention concerns an automotive protective mat1, also known as throw-in mat or protective mat, interacting with aconventional flooring system. This mat 1 comprises a microporousstiffening layer 2 (acoustical membrane). This layer 2 may be composedof several sheets. The overall air flow resistance is between 500Ns/m³–4000 Ns/m³, preferably between 500 Ns/m³–2000 Ns/m³. It isessential for this mat 1 that it is hydrophobic. In order to achieve anenhanced acoustical effectiveness a decoupling layer 6 is foreseenbetween the microporous stiffening layer 2 of the mat and the vehicleflooring 8. This decoupling layer 6 might be incorporated in the mat 1or constituted by the underlaying carpet or sound absorber of thevehicle floor. Further layers or sheets such as adhesive layers,non-skid layers, face fabrics or carpets and/or loft layers can be addedto the claimed mat.

The advantages of the claimed sound absorptive protective mat areapparent for the man skilled in the art and are to be seen in particularin the enhanced acoustical properties and the weight reduction of wholeflooring system.

1. Sound absorptive protective mat for use with a conventional motorvehicle flooring, in particular a multilayered assembly packagecomprising a microporous stiffening layer, which protective matcomprises a hydrophobic and air flow resistant layer having a total airflow resistance of 500 Ns/m³ to 4000 Ns/m³, whereby, in the assembledstate of the protective mat, with a motor vehicle flooring interactingmeans functioning as a decoupler, an air gap is generated between theprotective mat and the motor vehicle flooring.
 2. Sound absorptiveprotective mat according to claim 1 wherein the air flow resistant layeris a microporous layer with a bending stiffness of B=0.05 Nm to B=10.5Nm.
 3. Sound absorptive protective mat according to claim 1, wherein theprotective mat comprises a decoupler as interacting means.
 4. Soundabsorptive protective mat according to claim 2, further comprising aloft layer selected from the group consisting of a diecut needled felt,a diecut thermoplastic felt, a diecut non-hexa resinated felt, a moldedthermoplastic felt, a cast foam, and a diecut slab foam.
 5. Soundabsorptive protective mat according to claim 4, wherein the layers arebonded to each other by an air permeable adhesive layer.
 6. Soundabsorptive protective mat in combination with a conventional motorvehicle flooring, in particular a multilayered assembly packagecomprising a microporous stiffening layer, which protective matcomprises a hydrophobic and air flow resistant layer having a total airflow resistance of 500 Ns/m³ to 4000 Ns/m³, whereby interacting meansfunctioning as a decoupler generating an air gap are provided betweenthe protective mat and the flooring.
 7. Sound absorptive protective mataccording to claim 6 wherein the air flow resistant layer is amicroporous layer with a bending stiffness of B=0.05 Nm to B=10.5 Nm. 8.Sound absorptive protective mat according to claim 7, further comprisinga face fabric or carpet.
 9. Sound absorptive protective mat according toclaim 7, further comprising a loft layer selected from the groupconsisting of a diecut needled felt, a diecut thermoplastic felt, adiecut non-hexa resinated felt, a molded thermoplastic felt, a castfoam, and a diecut slab foam.
 10. Sound absorptive protective mataccording to claim 9, wherein the layers are bonded to each other by anair permeable adhesive layer.
 11. Sound absorptive protective mataccording to claim 3, wherein the layers are bonded to each other by anair permeable adhesive layer.
 12. Sound absorptive protective mataccording to claim 2, wherein the layers are bonded to each other by anair permeable adhesive layer.
 13. Sound absorptive protective mataccording to claim 1, wherein the layers are bonded to each other by anair permeable adhesive layer.
 14. Sound absorptive protective mataccording to claim 8, wherein the layers are bonded to each other by anair permeable adhesive layer.
 15. Sound absorptive protective mataccording to claim 7, wherein the layers are bonded to each other by anair permeable adhesive layer.
 16. Sound absorptive protective mataccording to claim 6, wherein the layers are bonded to each other by anair permeable adhesive layer.
 17. Sound absorptive protective mataccording to claim 1, wherein the hydrophobic and air flow resistantlayer has a total air flow resistance of between 500 Ns/m³ to 2000Ns/m³.
 18. Sound absorptive protective mat according to claim 6, whereinthe hydrophobic and air flow resistant layer has a total air flowresistance of between 500 Ns/m³ to 2000 Ns/m³.